DPP Home Technique Software Technique The first in a series of columns about controlling noise

Friday, April 10, 2009

Noise—Use It

The first in a series of columns about controlling noise


This Article Features Photo Zoom

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1 Original Image
Noise. It happens. What is it? Texture not native to the subject photographed, but introduced by the capture medium, editing process or output media. There are many reasons why it happens. There are things you can do to avoid it and things you can do to reduce it. (All are subjects for the future.) But once it’s there, noise often can be hard to separate from the detail of the subject; it may obscure it. Bottom line: It’s better not to have noise. If you need noise, you can always add it later. Need noise? Yes. There are many uses for noise. Today, we have more control over noise than at any other time in the medium.

Using Noise
Noise has its uses. Use noise to reduce banding. Banding found in digital files can be reduced, in some cases eliminated, with noise. Don’t confuse the linear banding sometimes found in different output devices with the irregular banding that follows color or tonal transitions in digital files as a result of aggressive image editing. If banding has been introduced during image editing, it’s better to go back upstream and reedit the file so that banding doesn’t occur, rather than adding noise to cure the side effect. Acquiring and editing in 16-bit eliminates a majority of banding. Consider noise as a solution only when this is either unavoidable or impossible

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2 Original Image With Noise
Use noise to restore a more naturalistic appearance to highly retouched areas or synthetic elements. Digitally rendered elements often are unusually smooth. This may produce an artificial appearance. A little noise can make these new elements look more real. In some cases, typically in high-contrast gradations, these new elements can be so smooth that various output devices (from monitors to printers) may have difficulty rendering them. A little noise often can be the cure. Use noise to unify multiple image sources with varying noise structures. One day, you may find you need to composite images with different noise characteristics, either from multiple sources (different resolutions and capabilities) or from one source used under very different conditions (different ISOs or exposure times). First, reduce noise in each source separately as much as possible without compromising image quality adversely. Next, using the noisiest element as a baseline, add noise to the other elements to make them seem as if they were all drawn from a single source used under the same conditions. In some cases, you may decide to have variances, small or large, in noise between different elements for creative effect. There are no easy formulas here. Simply look carefully and use your best judgment to generate an effect that’s pleasing or convincing to you.

Use noise as a creative effect. Many great photographers have used noise for creative effect; Michael Kenna and Sheila Metzner are two. Images may become more evocative because they contain noise. Many people use words like rough, gritty, nostalgic, impressionistic and mysterious to describe the effects of noise. For some, noise can be a gimmick (a meaningless element—a stylization unrelated to a way of seeing or relating to images, a distraction); for others, it can be a truly compelling artistic device (a meaningful element—a tool that enhances or creates a way of seeing and relating to images, a useful clue to artistic intention). In your images, one way or another, noise will be there or not. Either one is a choice and a statement, so think carefully about what level of noise is most appropriate for your images.

 

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